Liposomal nano-drugs based on amphipathic weak acid steroid prodrugs for treatment of inflammatory diseases

Abstract

Background: Steroids are the most efficacious anti-inflammatory agents. However, their toxicities and side-effects compromise their clinical application. Various strategies and major efforts were dedicated for formulating viable liposomal glucocorticosteroids (GCs), so far none of these were approved.

Objectives: To evaluate these approaches for formulating GC-delivery systems, especially liposomes, and with focus on the Barenholz Lab experience.

Methods: We developed PEGylated nano-liposomes (NSSL) remotely loaded with water-soluble amphipathic weak acid GC-prodrugs. Their remote loading results in high, efficient and stable loading to the level that enables human clinical use. We characterized them for their physical chemistry and stability. We demonstrated their therapeutic efficacy in relevant animal models and studied their pharmacokinetics (PK), biodistribution (BD) and pharmacodynamics advantages over the free pro-drugs.

Results: Our steroidal nano-drugs demonstrate much superior PK, BD, tolerability and therapeutic efficacies compared to the free pro-drugs and to most drugs currently used to treat these diseases. These nano-drugs act as robust immune-suppressors, affecting cytokines secretion and diminishing hemorrhage and edema.

Conclusions: The combination of improved physical-chemistry, PK, BD, tolerability and therapeutic efficacy of these steroidal nano-drugs over the pro-drugs “as-is” support their further clinical development as potential therapeutic agents for treating inflammatory diseases.

Keywords:

• Glucocorticosteroids
• steroid hemisuccinate derivatives
• drug delivery
• liposomes
• experimental autoimmune encephalomyelitis (EAE)
• rheumatoid arthritis (RA)
• lupus
• malaria

Acknowledgements

The help of S. Geller in editing this manuscript is gratefully acknowledged. This manuscript is dedicated to Prof. Pieter Cullis for winning the 2016 Journal of Drug Targeting Lifetime Achievement Award for his sustained excellence in Drug delivery and targeting fields. Firstly, like all “liposomolgists”, we thank Pieter’s for his contributions to the field at both the basic and applied research levels. I would like to refer to four major contributions (out of many) that I (Chezy Barenholz) personally and we in our lab consider as the major ones: (1) ³¹P NMR studies started during Pieter’s post-doctoral studies at Utrecht, which we and others are still using today to support XRD studies on the physical state of assemblies based on phospholipids. (2) Based on Hunt and Papahadjopoulos’ patent and publication describing the use of polycarbonate filters of defined pore-sizes for extrusion of MLV in-order to down-size them to the desired size. Doxil production is based on a similar concept. Pieter together with others, developed extruders to prepare liposomes of defined sizes in various volumes from a few milliliters to almost a liter scale. These extruders are now sold by Northern Lipids (Vancouver, Canada). Many of the labs in academia and industry that work with liposomes use one or more of these systems in their studies and/or development program. Pieter is now continuing this direction with his contribution to the development of the Nano-assembler, which is based on a microfluidics approach and is now sold by Malvern. (3) Pieter in 1985 started pushing forward the transmembrane pH driven remote loading approach. This development is based on previous work done by Deamer and coworkers in the 1970s such as Nichols and Deamer, 1976 paper for remote loading of catecholamines. Pieter and his team optimized this approach for the remote loading of a large repertoire of weak amphipathic bases mostly drugs. Myocet, a liposomal doxorubicin, anti-cancer drug approved for clinical use by the EMA, is a good example to a product based on this approach of pH driven remote loading using liposomes acidified by a very high intra-liposome (300 mM) concentration of citric acid at pH 4.0 (4). Pieter contributed and still contributing significantly to the inventions and development of novel cationic lipids having small head-groups and pKa close to neutrality. These cationic lipids enabled development of superior liposomal delivery systems for siRNA.

I (Chezy Barenholz) also want to thank Pieter Cullis personally for the inspiration he gave me, which encouraged me to dedicate more efforts to applied liposomology.

I and others in my lab, wish Pieter happy 70th birthday, many more years of good health, with a lot of fun and scientific creativity and productivity. We are all looking forward to his future contributions to the field and to science and technology in general.

Disclosure statement

Yechezkel Barenholz is a co-inventor on the two following patents: 1. Yechezkel Barenholz, Yaacov Naparstack, Yuval Avnir and Rina Ulmansky: “The use of Liposomal Glucocorticoids for Treating Inflammatory States”. US Patent 7,744 920, 29 June 2010; 2. Yechezkel Barenholz, Alberto A. Gabizon and Yuval Avnir: “Liposomal Compositions of Glucocorticoid and Glucocorticoid Derivatives”. US Patent 8,932 627, 13 January 2015.

Funding

We thank the Barenholz Fund for its support of all our studies presented in this review. The Hebrew University received royalties from Doxil^® sales until the patents expired. The Barenholz Fund was established with part of these royalties, and is used to support research in the Barenholz lab.